Spirocladia australiensis Huisman

Scientific Description

Habit and structure. Thallus pale red, to 2 cm tall, mostly erect. Percurrent axes bearing polysiphonous lateral branches every (1–) 10–15 segments. All axes with persistent pigmented trichoblasts arising 1 per segment in a spiral sequence. Primary axes 500–600 µm diam. near base [segment L:B 0.5–0.6], tapering gradually to 150–175 µm diam. near apices [segment L:B c. 1]. Trichoblasts to 1.7 mm long, 1–4 times subalternately branched near base, then with distal branches 5–7 cells long; lower 1–4 cells narrow, 10–20 µm diam., bearing markedly inflated cells to 75 µm diam., then tapering rapidly to a pointed apical cell. Apical cells often lost in older trichoblasts, which then have a broadly rounded apical cell.

Reproduction. Tetrasporangia arising in stichidial upper regions of trichoblasts, up to 13 per stichidium, 1 per segment in a spiral pattern, sequentially maturing, spherical, tetrahedrally divided, to 90 µm diam. Fertile region of stichidium with simple lateral branches to 7 cells long; branches basally narrow, inflated medially, then tapering to a sharp point.

Distribution. Known only from the Montebello Islands, north-western Australia.

[After J.M. Huisman in Algae of Australia: Marine Benthic Algae of North-western Australia, 2. Red Algae: 571–572 (2018)]